1. Field of the Invention
This invention relates to means and methods of reflecting or transmitting selected electromagnetic wavelengths from or to an object's surface. In particular, this invention relates to coatings which include a plurality of multilayer thin film particles.
2. Related Art
Lamellar pigment particles comprised of a plurality of layers, where adjacent layers have different indices of refraction, have been employed in coatings to reflect light from a surface. However, the quality of these known coatings is insufficient to meet the present day demands for the transmission or reflection of one or more sharp spectral peaks.
When limiting an object's observability, one generally wishes to either (1) reflect very little of a particular wavelength included in an interrogating search beam, such as a laser, but reflect at other wavelengths so that the object matches the background environment, (2) modify an object's thermal radiance by strongly suppressing selected infrared wavelengths, (3) match the emissions from an object to its surroundings by suppressing selected visible, infrared or ultraviolet wavelengths or (4) combinations of the above three techniques. In many cases, the emissions to be suppressed are spectrally narrow and suppression applied outside these narrow bands negates coating effectiveness.
Prior art coatings which incorporate lamellar particles have offered only relatively broad spectral peaks or have caused substantial diffuse reflectance. The prior art means of construction do not allow for the achievement of narrow spectral structures. Such condition does not provide effective observability reduction against current optical sensing techniques.